Vented hood on the cheap
08-12-2013, 06:41 PM
#31
Really? A luxury barge that will never see the track? Do you think your typical Aston buyer would like louvers? This is form over function.
BTW, here's a Aston race car:
Again, is anyone going to track this thing? This is a bad tuner bodykit. Might as well be a Veilside kit.
You do realize the Evora is mid-engine right? No engine in the front to restrict air flow. Also, I'd venture to guess the whole front undertray is completely sealed leaving only those holes out the hood for the air to escape. It's essentially ducted.
And here's a Lotus GTE road car, though in all honesty, I think the flaps in the holes are merely to guide the airflow.
Evo X's have the same thing. You do realize the flow regime is completely different in that area as compared to the hood right? It's very turbulent due to the dirty air coming off the wheel and wells.
Here's one image of a lotus. Notice the wheels have a lower pressure area right behind them. Right where the vents are on the STI and Evo X.
Why are you even talking about the rear? It's a completely different problem statement as the flow at the rear of the car is completely different than at the front.
Okay, I'll go with you don't THINK the louvers are beneficial compared to a simple cutout, but I disagree based on observation; so without even trying to derive the fluid flow equations.
Also consider this, the hood and raked. So the back edges of the holes are at a higher location than the front edges. Said another way, the hole is tilted forward. I imagine this will make air want to go IN the hole. And this would do exactly as you described as to what others have experienced which is to reduce underhood temps.
Those equations are actually derived from the momentum equation for fluid flow, so that's more college level fluid mechanics.
So you value looks over performance. Got it. FYI, I think these cars are ugly as sin, but they are a couple of the fastest time attack cars in the world
You also do realize this is a 'track' hood that is only used for the track right? I know guys who have spare trunks with wings. They swap on the trunk with the wing for the track, and put the stock trunk back on for DD use.
I haven't seen any physics counterpoints yet. I'm done replying unless you can find something along the lines of a technical paper or CFD analysis that proves your point of a open cutout being as effective as the louvers when trying to extract air from an unducted volume such as the engine bay or wheel well.
BTW, here's a Aston race car:
Again, is anyone going to track this thing? This is a bad tuner bodykit. Might as well be a Veilside kit.
You do realize the Evora is mid-engine right? No engine in the front to restrict air flow. Also, I'd venture to guess the whole front undertray is completely sealed leaving only those holes out the hood for the air to escape. It's essentially ducted.
And here's a Lotus GTE road car, though in all honesty, I think the flaps in the holes are merely to guide the airflow.
Here's one image of a lotus. Notice the wheels have a lower pressure area right behind them. Right where the vents are on the STI and Evo X.
I'm not arguing that louvers aren't useful. I'm saying that I don't think a few puny louvers are going to make up for only having those small cut outs. Louver all six panels and get rid of the AC and you might be in business. But for simplicity, I'd just do the six cuts and use rubber trim strips to help either with leading edge or lagging edge.
Or get some cheap aluminum duct work and vent the backside of the radiator out to a big center cut. Louvers optional.[/size]
Or get some cheap aluminum duct work and vent the backside of the radiator out to a big center cut. Louvers optional.[/size]
Also consider this, the hood and raked. So the back edges of the holes are at a higher location than the front edges. Said another way, the hole is tilted forward. I imagine this will make air want to go IN the hole. And this would do exactly as you described as to what others have experienced which is to reduce underhood temps.
You also do realize this is a 'track' hood that is only used for the track right? I know guys who have spare trunks with wings. They swap on the trunk with the wing for the track, and put the stock trunk back on for DD use.
For the record, I think the louvers are "fine" and if the thread was, "hey, I had time and was bored and made some slits in my hood because I think it's cool" I'd be like, "cool bro." But I wanted to bring out physics counterpoints and questions to the efficacy of this mod so that the casual reader would have a counterpoint to consider.
The comments on the original link basically echo the criticism in this thread. And did you really pay $200 for that hood just to do that do it?! That's not free.
The comments on the original link basically echo the criticism in this thread. And did you really pay $200 for that hood just to do that do it?! That's not free.
08-12-2013, 06:44 PM
#32
Again, there has to be consideration to form on a production car sold to the public. Look at any of the pure race cars I linked.
08-12-2013, 06:46 PM
#33
Actually, now that I think about it, your design is backwards.
I'd agree with it if you cut the front edges and bent the flaps DOWNWARD into the recess to draw and channel air up out of the holes. You could foil tape the sides in the hole of you needed to. But maybe not even necessary.
I'd agree with it if you cut the front edges and bent the flaps DOWNWARD into the recess to draw and channel air up out of the holes. You could foil tape the sides in the hole of you needed to. But maybe not even necessary.
08-12-2013, 06:47 PM
#34
I disagree with your pseudo-engineering. None of the examples you cite use louvers that look like yours.
If you can find examples of louvers that rise above the hood plane and are open on the sides, then I might buy your argument. But not with the hacking of the original build.
I'd say that was a waste of $200 and two hours.
Going with louver theory, I'd say cut out front four holes and make a recessed set of louvers out of wood or plastic if you like. Cover with a screen to make it look more finished. There are plenty of engineered examples of that.
So yes, louver theory.
No, hacked flaps that tuft up with open sides.
If you can find examples of louvers that rise above the hood plane and are open on the sides, then I might buy your argument. But not with the hacking of the original build.
I'd say that was a waste of $200 and two hours.
Going with louver theory, I'd say cut out front four holes and make a recessed set of louvers out of wood or plastic if you like. Cover with a screen to make it look more finished. There are plenty of engineered examples of that.
So yes, louver theory.
No, hacked flaps that tuft up with open sides.
I contend the flaps are more effective than just the open hole.
08-12-2013, 06:53 PM
#36
And let me ask you this, how do you simply add 'sides'? You can't. You'd have to add material. That takes away from 'simple' doesn't it? Seeing how you read the comments, you'd see the original intent was to design proper drop-in louvers with sides and all. But that takes a lot more time and money.
I contend the flaps are more effective than just the open hole.
I contend the flaps are more effective than just the open hole.
Or do what the 2nd poster in the thread did and buy plastic inserts as the drop in louvers.
08-12-2013, 07:06 PM
#37
So you're saying to buy a track hood for $200 and hack it up for theoretical, but unproven magnitude of benefit.
Does it reduce engine temps by 1 degree? 5 degrees? 10 degrees? Is $200 worth one degree cooling? We know that turning on the heat allows more cooling than that.
What about rigging a mister (like STIs used to have) to mist the radiator and accelerate cooling?
I am saying that I think proper louvers work. I am also saying that I have serious doubt regarding the magnitude of benefit of your published "louver" modification. And that I have serious, serious doubt regarding the cost effectiveness of your cooling mod given the cost of the hood.
I wouldn't pay $200 for one degree cooling when engine temps are in the "adequate" range.
Answer me this: Do you replace your coolant with DI water + water wetter? Higher capacity to extract heat.
So if the vent hood mod costs $200 and lowers temps by 1 degree, but using DI water plus water wetter lowers it by 5 degrees for $5, which would I pick?
Does it reduce engine temps by 1 degree? 5 degrees? 10 degrees? Is $200 worth one degree cooling? We know that turning on the heat allows more cooling than that.
What about rigging a mister (like STIs used to have) to mist the radiator and accelerate cooling?
I am saying that I think proper louvers work. I am also saying that I have serious doubt regarding the magnitude of benefit of your published "louver" modification. And that I have serious, serious doubt regarding the cost effectiveness of your cooling mod given the cost of the hood.
I wouldn't pay $200 for one degree cooling when engine temps are in the "adequate" range.
Answer me this: Do you replace your coolant with DI water + water wetter? Higher capacity to extract heat.
So if the vent hood mod costs $200 and lowers temps by 1 degree, but using DI water plus water wetter lowers it by 5 degrees for $5, which would I pick?
08-13-2013, 04:55 AM
#38
Former Moderator
CKit, you're being pretty harsh in this thread. This is the r&c forum and homemade mods and experimentation are the order of the day. We should be encouraging people to experiment and not be afraid of looking different. It looks to me like his louvers would be better than just an open hole and an open hole works well too because of the low pressure on the upper surface of the hood. Heat is the S2000's bane and any effort to remove it should be applauded.
08-13-2013, 08:46 AM
#39
I agree I'm being pretty harsh.
I think louvers are great.
I am not disagreeing with the concept or even the execution.
I'm disagreeing with the pseudo-physics sell.
Heat is the bane, but I'm looking for more data to get a sense for the magnitude of the benefit.
And by talking it out, we can come up with a better V2 design.
Do you want a place where people post all kinds of unvetted opinions or data to back up what their theory states.
So the things I'd look for is a back to back heat test of stock hood and little louvers or else it's just a novelty.
I would love for there to be a good DIY solution. I just don't think that this is it. I think there would have to be more surface area, sealed louvers and some internal ducting to really make it effective.
I would have loved it if the thread was a "hey, I'm thinking of doing this for venting, any suggestions or feedback on improving the design" rather than a "I've made this awesome physics design that uses race elements and you can do this too if you need cooling because something is better than nothing... but I haven't tested how much of a difference it makes, but trust me it's awesome."
The good news is that the back to back testing should be pretty easy with what he has now. First step would be to see how much benefit it gives over an OEM hood.
So if we've established that this is just an exercise in hood venting and not a project for maximum cooling (where we'd add potentially bigger / faster fans to the rad, mister spray to the front (I have one on the turbo car), water wetter, no AC, nose boxing, and removal of the stock air box to improve unimpeded flow to the vents), then I think we have some real potential to improve this design.
Seems like flap down louver might work better than unboxed flap up. And for the same number of cuts.
I think louvers are great.
I am not disagreeing with the concept or even the execution.
I'm disagreeing with the pseudo-physics sell.
Heat is the bane, but I'm looking for more data to get a sense for the magnitude of the benefit.
And by talking it out, we can come up with a better V2 design.
Do you want a place where people post all kinds of unvetted opinions or data to back up what their theory states.
So the things I'd look for is a back to back heat test of stock hood and little louvers or else it's just a novelty.
I would love for there to be a good DIY solution. I just don't think that this is it. I think there would have to be more surface area, sealed louvers and some internal ducting to really make it effective.
I would have loved it if the thread was a "hey, I'm thinking of doing this for venting, any suggestions or feedback on improving the design" rather than a "I've made this awesome physics design that uses race elements and you can do this too if you need cooling because something is better than nothing... but I haven't tested how much of a difference it makes, but trust me it's awesome."
The good news is that the back to back testing should be pretty easy with what he has now. First step would be to see how much benefit it gives over an OEM hood.
So if we've established that this is just an exercise in hood venting and not a project for maximum cooling (where we'd add potentially bigger / faster fans to the rad, mister spray to the front (I have one on the turbo car), water wetter, no AC, nose boxing, and removal of the stock air box to improve unimpeded flow to the vents), then I think we have some real potential to improve this design.
Seems like flap down louver might work better than unboxed flap up. And for the same number of cuts.
10-01-2013, 09:34 PM
#40
I agree I'm being pretty harsh.
I think louvers are great.
I am not disagreeing with the concept or even the execution.
I'm disagreeing with the pseudo-physics sell.
Heat is the bane, but I'm looking for more data to get a sense for the magnitude of the benefit.
And by talking it out, we can come up with a better V2 design.
Do you want a place where people post all kinds of unvetted opinions or data to back up what their theory states.
So the things I'd look for is a back to back heat test of stock hood and little louvers or else it's just a novelty.
I would love for there to be a good DIY solution. I just don't think that this is it. I think there would have to be more surface area, sealed louvers and some internal ducting to really make it effective.
I would have loved it if the thread was a "hey, I'm thinking of doing this for venting, any suggestions or feedback on improving the design" rather than a "I've made this awesome physics design that uses race elements and you can do this too if you need cooling because something is better than nothing... but I haven't tested how much of a difference it makes, but trust me it's awesome."
The good news is that the back to back testing should be pretty easy with what he has now. First step would be to see how much benefit it gives over an OEM hood.
So if we've established that this is just an exercise in hood venting and not a project for maximum cooling (where we'd add potentially bigger / faster fans to the rad, mister spray to the front (I have one on the turbo car), water wetter, no AC, nose boxing, and removal of the stock air box to improve unimpeded flow to the vents), then I think we have some real potential to improve this design.
Seems like flap down louver might work better than unboxed flap up. And for the same number of cuts.
I think louvers are great.
I am not disagreeing with the concept or even the execution.
I'm disagreeing with the pseudo-physics sell.
Heat is the bane, but I'm looking for more data to get a sense for the magnitude of the benefit.
And by talking it out, we can come up with a better V2 design.
Do you want a place where people post all kinds of unvetted opinions or data to back up what their theory states.
So the things I'd look for is a back to back heat test of stock hood and little louvers or else it's just a novelty.
I would love for there to be a good DIY solution. I just don't think that this is it. I think there would have to be more surface area, sealed louvers and some internal ducting to really make it effective.
I would have loved it if the thread was a "hey, I'm thinking of doing this for venting, any suggestions or feedback on improving the design" rather than a "I've made this awesome physics design that uses race elements and you can do this too if you need cooling because something is better than nothing... but I haven't tested how much of a difference it makes, but trust me it's awesome."
The good news is that the back to back testing should be pretty easy with what he has now. First step would be to see how much benefit it gives over an OEM hood.
So if we've established that this is just an exercise in hood venting and not a project for maximum cooling (where we'd add potentially bigger / faster fans to the rad, mister spray to the front (I have one on the turbo car), water wetter, no AC, nose boxing, and removal of the stock air box to improve unimpeded flow to the vents), then I think we have some real potential to improve this design.
Seems like flap down louver might work better than unboxed flap up. And for the same number of cuts.
If you would have bothered to read my NACA duct article, you would have read that I did test the vented hood at the track. Here, I'll link it to make it easy on you:
http://www.motoiq.com/MagazineArticl...r-Testing.aspx
If you want just the summary: stock hood, ambient temp = 92F, oil temp = 117C; vented hood, ambient temp = 102F, oil temp = 117C.
If you go back and read the comments on the vented hood article, a guy who does CFD for a living provided constructive criticism. Notice the word constructive.
As for the answer to the effectiveness of just open holes in the hood:
https://www.s2ki.com/s2000/topic/877...t__p__20812917
"I have hood vents, but they are ONLY for looks, and actually increased my engine ccolant temps at the track. I have only 3 vents cut on the passenger side, and my coolant temps went up to 225F at a track day last year. Another S2000 owner at the same track event hit 250F with his hood vented with the 4 smaller vents near the windshield."
In reading the comment from CFD guy, you'll understand why this happened. You know, you can learn quite a bit by just reading. Based on feedback from the CFD guy, a V2 can be done with better effectiveness. But hey, it took a V1 to get the ball rolling. Plus, my concept, though not perfect, did improve cooling system performance whereas the simple holes in the hood actually DECREASED performance per Gernby.